As talks aimed at a comprehensive nuclear deal with Iran continue, with principals from Iran and world powers meeting in Vienna this week, two recent analyses of the negotiations have compared the talks to a “Rubik’s Cube.”

A May 9 report from the International Crisis Group (ICG) entitled, “Iran and the P5+1: Solving the Nuclear Rubik’s Cube,” offers 40 recommended action items that Iran and the P5+1 (the US, UK, France, China and Russia plus Germany) could agree to implement in a comprehensive deal. Today the United States Institute of Peace (USIP) also held a panel discussion called, coincidentally, “The Rubik’s Cube of a Final Iran Deal,” moderated by Colin Kahl, the top Middle East policy official at the Defense Department for most of Obama’s first term, and featuring Robert Einhorn, who served as the State Department’s special advisor on non-proliferation and arms control until less than a year ago, Joe Cirincione, the president of the Ploughshares Fund, and Alireza Nader, an Iran expert at the RAND Corporation.

There’s a clear sense in both analyses that a deal is reachable. Cirincione rightly pointed out at the USIP event that the current talks are “the closest we’ve come to an agreement, ever,” and predicted that “absent some unforeseen event, we are going to get a deal.” Indeed, the very existence of something like the ICG report, a specific and detailed look at what a deal might actually contain, would have appeared presumptuous even six months ago but now seems very reasonable given the progress that has already been made.

However, optimism aside, a great deal of work still needs to be done before a deal can be finalized. The level of detail contained in the ICG report speaks to the complexity involved in the negotiations. The ICG recommends, for example, an immediate cap on Iranian uranium enrichment of 6400 Separative Work Units (SWU, a measurement of enrichment capacity that incorporates both the number and technological advancement of operational centrifuges) per year, which is a steep cut from Iran’s current 9000 SWU/year capacity (that Iran sees as already too low), and one that the Iranians may be unwilling to make. That cap would then be lifted, over 8-10 years, to around 19,000 SWU/year, an increase that could theoretically reduce the time it would take Iran to manufacture a nuclear weapon if it chose to pursue that goal. Of course, it remains to be seen whether Iran and the P5+1 would agree to those terms.

The ICG framed its recommendations around four points:

constraining any Iranian capacity to build a nuclear weapon;

implementing a stringent monitoring and verification system on Iran’s nuclear program,

establishing concrete negative consequences for a breach of the deal by either side;

and establishing positive consequences for compliance.

But the ICG’s recommendations, and the discussion on the USIP panel, make it very clear that these objectives will be difficult to meet in a way that satisfies both parties. The two sides disagree on even basic elements of the talks; as Kahl explained, the Iranian government rejects the P5+1’s continued focus on Iranian “breakout capacity” because it has officially sworn off of any military application of its nuclear program. The P5+1 does not accept those assurances, but Iran also has legitimate questions as to why other countries with civilian nuclear programs have not been subject to the same requirements that Iran has faced.

The USIP panel seemed to reach a general consensus that the biggest remaining hurdles to a comprehensive deal revolve around Iran’s uranium enrichment program. This includes both Iran’s capacity for enrichment and the amount of enriched uranium it will be allowed to stockpile; the level of access that Iran will permit to the International Atomic Energy Agency (IAEA) and its inspectors; and the timing of and conditions for sanctions relief.

The P5+1 are seeking to maximize the limits on Iran’s nuclear program and the IAEA’s access to Iranian nuclear sites while maintaining sanctions at a high level for a considerable period of time, perhaps decades. Iran, obviously, is seeking the opposite - minimal limits on its nuclear program in return for considerable sanctions relief and only a short period in which its program is subject to international monitoring. As the ICG report put it, “it would appear that the P5+1’s maximum - in terms of both what it considers a tolerable residual Iranian nuclear capability and the sanctions relief it is willing to provide - falls short of Iran’s minimum.”

The single biggest complication to these talks is the utter lack of trust on both sides. As Nader argued, mutual trust is not a requirement for success and the lack of trust can be worked around with stringent inspections requirements and firm commitments to agreed-upon sanctions relief. But that lack of trust adds considerable complexity and difficulty to the negotiations. Iran is ultimately being asked to prove a negative, that it has no nuclear weapons program, and because the P5+1 do not trust Iran to uphold its promises, demands for monitoring requirements and caps on nuclear capacity may simply be too much for Iran to accept.

This is particularly true given a domestic political environment that Nader termed “poisonous,” with Iranian hardliners increasingly concerned about President Hassan Rouhani’s commitment to protecting Iran’s interests in these negotiations, and Supreme Leader Ayatollah Ali Khamenei’s support for the talks vulnerable to shifting political winds.

Yet failed talks could be disastrous for both sides, according to the ICG. Failure now would make another attempt at negotiations very unlikely, would result in new punitive measures against Iran (including new sanctions on an already sputtering economy, and potential military strikes on Iranian nuclear sites), and could ultimately push Tehran to rush for a nuclear weapon, something which everyone, including Iran, says they don’t want.

About the Author:Derek Davison is a Washington-based researcher and writer on international affairs and American politics. He has Master's degrees in Middle East Studies from the University of Chicago, where he specialized in Iranian history and policy, and in Public Policy and Management from Carnegie Mellon University, where he studied American foreign policy and Russian/Cold War history. He previously worked in the Persian Gulf for The RAND Corporation.